The present invention relates to reclosable plastic bags of the type in which perishable food products and other goods are packaged for sale to consumers in retail outlets. More specifically, the present invention relates to a method for concurrently manufacturing plastic bags with gussets in the pouch of the bag.
The present invention relates to improvements in the package-making art and may be practiced in the manufacture of reclosable plastic bags and packages of the type that may be used for various consumer products. Such packages often include a form of peel-seal to render the package moisture-tight and/or airtight prior to the initial opening, and/or for use as a tamper-evident seal. A zipper means protects any remainder of the product therein after the initial opening.
The indicated art is fairly well-developed but nevertheless remains open to improvements contributing to increased efficiency and cost-effectiveness. In the prior art, McMahon et al. (U.S. Pat. No. 4,909,017) discloses a method for making a package with a reclosable fastener on a form-fill-and-seal machine. Prior to entering the form-fill-and-seal machine, zippers are attached to the surface of the film used to make the package, with the zippers transversely attached to the running direction of the film at bag-length intervals. Only one of the interlocking profiles of the zipper is attached by its flange section to a surface of the film with the other interlocked profile facing upwardly or, in other words, inwardly toward the interior of the bag to be formed. The film is advanced to the form-fill-and-seal machine and drawn down over a forming collar and about the filling tube, with the longitudinal side edge margins of the film brought together and seamed with a fin seal to form a tube. Cross-seals are made on the tube to join the unattached profile of the zipper to the film and to form the ends of the bag and following bags.
The commonly assigned patent application xe2x80x9cProcess and Apparatus for Forming Packaging Bags With a Fastenerxe2x80x9d (U.S. Ser. No. 09/633,944, allowed Jul. 26, 2002) discloses a method in which a slider for opening and closing the fastener is attached to the fastener before the fastener is attached to the film being advanced to the form-fill-and-seal machine. Various components of the form-fill-and-seal machine allow the fastener with attached slider to advance in the machine and to be part of the formed reclosable bag.
The commonly assigned patent application xe2x80x9cMethod of Forming Gusseted Reclosable Bagsxe2x80x9d (U.S. Ser. No. 09/726,731, allowed Oct. 2, 2002) discloses a method for forming the reclosable packaging with gussets. In the method, first and second carrier webs are provided which include discrete mating zipper profile sections. The zipper profile sections are separated from each other on the carrier web by zipper-free sections of the carrier web. The carrier webs are attached to the first ends of first and second bag wall films as the bag wall films, respectively, are brought together. The bag wall films may be separate webs or a single longitudinally folded web. The carrier webs are formed of thinner-gauge plastic film than the bag wall films. The first and second bag wall films and the first and second carrier webs are cross-sealed with the carrier webs being sealed through the zipper-free sections of the web, and the assembly is transversely cut through the cross-seals to form a bag. A second end gusset is formed in the bag by reverse-folding the second end of the bag walls. If the bag walls are formed from separate films, the films must be connected either by simply sealing the second ends of the bag wall film to each other or by sealing a folded second end web to the second ends of both bag wall films. Side gussets are then formed by pushing in the end parts of the bag walls as well as the zipper-free sections of the carrier web between the open zipper sections.
An improvement in the above methods and the apparatus used in the above methods is the ability to provide side gussets in the pouch portion of the reclosable bags to be formed, in which the side gussets are formed in the pouch portion or in which a length of gusset material is sealed in the pouch portion in a manner that would not restrict the opening of the reclosable bag nor affect the use of the interlocking elements of the zipper of the bag.
Accordingly, the present invention relates to a method for producing reclosable plastic bags with expandable gussets in which the bags are manufactured in an efficient manner that readily lends itself to automated production.
In a first embodiment of the present invention, a first interlocking profile of a length of zipper is attached by one of its flanges to a mid-portion of a continuous length of bag-making film at a direction transverse to the running direction of the film, while leaving side margins of film on opposite ends of the zipper so that the combined length of the side margins of film is greater than the length of the zipper.
As the bag-making film is advanced, the side margin on one end of the zipper is sealed to the side margin on an opposite end of the zipper to form a fin seal. The fin seal forms the longitudinal seam of a tube with an inside surface of the rear wall of the tube facing the unattached profile of the zipper. As the tube is advanced, retractable gusset-forming wheels wedge and indent the side margins to form side gussets such that the base of the formed side gussets defines the longitudinal borders of the rear wall.
For a zipper with an inserted slider, the retractable gusset-forming wheels form the side gussets adjacent the interlocking elements of the zipper to allow the slider to fully open and close the interlocking elements. The amount and size of the gusset-forming wheels extending into each side margin may vary to produce multiple side gussets of different sizes in each side margin of the film. The unattached interlocking profile of the zipper is sealed by its flange section to an inner surface of the rear wall that is formed by the remaining portions of the side margins. A section of the gussets is sealed to the rear wall adjacent the interlocking elements of the zipper to form a border area below the zipper. The border area allows access to the interior of the bag only through the zipper area of the bag.
For a zipper without a slider, the tube proceeds in a bag-forming direction to a sealing section. The sealing section seals the unattached zipper profile by its flange to a face of each side gusset and to an inner surface of the rear wall of the tube in which the longitudinal borders of the rear wall are defined by the base of the side gussets. An opposite face of each side gusset is sealed to the inner surface of the rear wall as a border area to ensure that access to the contents of the formed reclosable bag is through the zipper only. The opposite face of each side gusset is sealed to the rear wall parallel to and below the sealing of the zipper to form the border area at and below the zipper.
The sealing section forms end stops on the zipper to prevent the zipper from separating and to prevent tearing into the bag at the ends of the zipper. The end stops also retain the slider on the zipper when the slider is used to open and close the bag. After the sealing operation, the sealing section separates the tube with an internal cutting device to form a reclosable bag and seals the film to form an end seal of a preceding reclosable bag. Another end seal may be formed as a part of a tamper-evident section of film adjacent the zipper of the reclosable bag.
In a second embodiment of the present invention, a first continuous length of bag-making film and a second continuous length of bag-making film are fed toward each other in a bag-forming direction from their respective supply rolls. The first length of film is fed to become the upper web and the second length of film is fed to become the lower web of the formed reclosable bag. First and second lengths of gusset material, each in the shape of an elongated tube, are positioned on the lower web transverse to the bag-forming direction. A first end of each length of gusset material is tack-sealed to the lower web.
A zipper is positioned on the lower web and on the first end of the lengths of gusset material and, if the zipper includes a slider, with the interlocking elements of the zipper adjacent the ends of the gusset material. A set of rollers advances the webs while flattening the gusset material. The flanges of the zipper are sealed to the upper and lower webs and over the first end of the lengths of gusset material.
In a first variation of the second embodiment of the present invention, the upper and lower webs are fed toward each other to provide film extensions on an opposite side of the zipper from the ends of the gusset material.
In a second variation of the second embodiment of the present invention, the tubular lengths of gusset material are fed between the flanges of the zipper. For the second embodiment and its first and second variations, the upper and lower webs, as well as the second end of the tubular lengths of gusset material, are sealed to form an end seal or a bottom seal of the reclosable bag.
The assembly of the webs and the zipper is advanced and transversely cut to the bag-forming direction and sealed to form a transverse seal at a leading edge. Also at the leading edge, the tubular length of gusset material is cut along a centerline of the length to form a side gusset while sealing the cut section of the gusset material to the webs as part of the transverse seal. The assembly of the webs, the zipper and the gusset material are advanced to a reclosable bag width in which a trailing edge is cut in the webs, in the zipper and in the gusset material to form the reclosable bag with a second side gusset at the trailing edge. Also at the trailing edge, the cut section of the gusset material is sealed to the webs as part of a transverse seal.
After the bag is filled with a consumer product, the open ends of the film extensions may be sealed to provide a tamper-evident feature which encloses the zipper. A weakness area is formed in the film extensions to tear away the film in order to access the zipper during an opening of the reclosable bag.
In a third variation of the second embodiment of the present invention, a semi-elliptical length of gusset material is inserted between the upper and lower webs and in a slit area of the first and second lengths of gusset material to form a bottom gusset of the reclosable bag.